Dating is all about making snap judgments, and scientists have located where in the brain those decisions are made.

Researchers at Trinity College in Dublin, Ireland recruited 151 heterosexual college students for a speed dating study with a twist. They asked 39 of the participants to have their brains scanned with a functional MRI (fMRI) prior to the event while the students looked at pictures of their potential suitors. The participants were asked to rate the pictured individuals on a scale of one to four on whether they would be interested in pursuing dates with them. The students also rated each of the pictured individuals on attractiveness and likeability. These ratings were public and made available to all of the participants as they were scanned.

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During the speed dating event, the students were allowed to mingle and chat with one another for no longer than five minutes each. At the end, they filled out a form indicating which people they wanted to see again, and for those who mutually agreed, contact information was exchanged.

Not surprisingly, the students were pretty adept at knowing which people they would be interested in pursuing just by looking at their picture. But when the researchers matched up the brain scans with the real-life dating decisions, they found that a certain region of the prefrontal cortex was almost always activated when participants had an immediate attraction to a person.

And the appeal went beyond the physical. Known as the dorsomedial prefrontal cortext (dmPFC), the region includes two sub-regions; the paracingulate cortex which makes calculations about a person’s attractiveness, and the rostromedial prefrontal cortex (rmPFC located close to the eyes), which is activated when the brain senses a disconnect between its immediate assessment of attractiveness and other people’s perceptions. This is the part of the brain that calculates whether, for example, someone is right for you, regardless of what other people think. In other words, the authors write in the Journal of Neuroscience, the rmPFC, “correlated not with partners desired by everybody, but with those who were especially desirable to specific participants.”

The people who were most attractive overall also triggered activation of the ventromedial PFC (vmPFC), an area that has previously been found to react to appealing faces. However, this activation didn’t predict pursuit— perhaps because of the overlaying effect of the rmPFC that included an evaluation that the beauties and cuties might be unattainable or because some people don’t find the most conventionally attractive people most attractive to them.

The findings highlight the importance — and inevitability — of first impressions. Daters knew almost immediately whether or not they liked someone and that initial perception had a great deal to do with whether the person was ultimately chosen as a date. Daters also apparently felt they could judge “likability” based on appearance, which may account for why “girl next door” or “guy next door” types tend to get asked out more than those with model-like good looks.

So while we don’t exactly judge people on their appearance, how people look is the first cue that we grab on to in order to start building an impression, at least when it comes to finding dates. “Judgments about romantic relationships thus seem to be formed within seconds of seeing a potential partner, but also depend on a complex mix of evaluations about physical and psychological compatibility,” write the authors. Which means maybe we really aren’t that shallow after all.